The present invention concerns an arresting brake device with triggering equipment for elevators which, being guided by guide rails, move in upward and downward directions of travel and which, being monitored by a speed limiter, can be braked by this arresting brake device by a braking force, which force is different in upward and downward directions of travel, on speed limit values being exceeded.
As used herein, different braking force means that the braking force, and thus the retardation in the case of an emergency braking in an upward direction, shall be substantially smaller in the upward direction than in a downward direction for physical reasons and for reasons of human tolerability.
The simplest technical, although expensive, solution for the fulfillment of this demand consists in arranging two conventional arresting devices one above the other in opposite direction of function, as disclosed in European patent document EP 0 440 839. In this solution, abutment screws are provided, which are to enable the setting of different braking forces. It is not, however, evident from the schematic illustration, the description and the claims how a defined braking force is to result, since the oppositely disposed brake shoe and the sliding underlay are represented as rigid elements. A defined braking force can result by the available travel of the respective braking wedge together with the resilient counterforce of a brake shoe lying opposite thereto or together with the resilient counterforce of the sliding underlay of the respective brake wedge. The first solution is known from German patent document DE 27 44 986 and the second solution is known from European patent document EP 0 432 634, wherein the latter illustrates a double arresting device with two individual wedges, which lie opposite one another in reverse direction, with separate abutment screws.
As a further known constructional principle for double-acting arresting devices, those with a double eccentric are to be mentioned. Such a solution is known from the German patent document DE 805 782. According to this solution, a part denoted as a double-acting eccentric is used in the form of a circular segment with a radius which is greater than the radius of rotation. Thereby, a wedging-in of the guide rail against a spring device lying opposite thereto takes place during the moving-in, wherein the strength of the latter yields the magnitude of the braking force. The spring device is adjustable, but acts equally strongly in both directions of moving-in of the eccentric, which then also results in the same retardation values for both directions of travel.
An article in LIFTREPORT (Volume 5/91, page 38) describes an arresting brake BF.times.3 acting with different braking force in both directions of travel. A triggering device acting by way of a cable pull and a cable looping is operatively connected with a respective eccentric disc on each side of the elevator car. The eccentric discs have two flats that act as abutments and stop the rotational movement in the case of a triggering. On a triggering, both the eccentric discs are rotated up to these abutment surfaces in clockwise or counterclockwise sense according to direction of travel. The radius, which increases with the rotation, of the eccentric discs compresses a compression spring lying opposite, whereby the braking effect then arises. The angle of rotation is smaller for a braking in an upward direction of travel than in a downward direction of travel and the braking effect and thus the retardation are, as desired, also smaller in the upward direction. The ratio of the two braking effects in the upward direction and the downward direction of travel relative to each other is given by the geometric dimensions of the eccentric discs and can no longer be varied subsequently. The braking force is adjustable only generally by the adjustable spring. Due to the rolling path of the eccentric discs, a relatively long reaction travel results up to the full braking effect.